An MRI apparatus measures an NMR signal generated by atomic nucleus spin that comprises tissue of an object in particular to a human body and creates images of shapes and functions of human head, abdomen, four limbs, etc, two-dimensionally or three-dimensionally. During imaging, phase encoding that varies depending on the gradient magnetic field is given to an NMR signal, and frequency encoding is performed for the NMR signal, and it is measured as time-series data. The measured NMR signal is reconstructed to an image by performing a two-dimensional or three-dimensional Fourier transform.
Reception coils that receive an NMR signal has a multi-element coil that includes multiple elements. An MRI apparatus to which a multi-element coil can be connected determines elements to be used for measuring in the light of a disposed position, an imaging range, a signal strength, etc. of the respective elements (for example, see PTL 1 and PTL 2).
By the way, because an NMR signal to be received (reception signal) is an analog signal, A/D conversion needs to be performed. When the number of A/D converters (channels) is equal to or less than the number of elements comprising the multi-element coil, reception signals received by the respective elements are arbitrarily reduced to equal to or less than the number of channels by synthesizing the signals using a synthesizer and are output to the respective A/D converters.
In this case, if the elements that synthesize the reception signals are fixed, this cannot be addressed flexibly according to changes of imaging conditions, in particular an imaging range. Also, it takes much time and efforts for a user to change a synthetic form according to the imaging conditions, and, in addition, it is also difficult to keep quality of images to be output.
In order to solve these problems, for example, a method that maintains an index to determine image quality by associating reception signals with all the synthesizable combinations in advance and determines a combination of the reception signals to be synthesized according to an imaging range and desirable image quality is provided (for example, see PTL 3).